Field effect transistor devices with self-aligned source/drain contacts and gate contacts positioned over active transistors

ABSTRACT

A method of forming a transistor device is provided. The method includes forming a plurality of gate structures including a gate spacer and a gate electrode on a substrate, wherein the plurality of gate structures are separated from each other by a source/drain contact. The method further includes reducing the height of the gate electrodes to form gate troughs, and forming a gate liner on the gate electrodes and gate spacers. The method further includes forming a gate cap on the gate liner, and reducing the height of the source/drain contacts between the gate structures to form a source/drain trough. The method further includes forming a source/drain liner on the source/drain contacts and gate spacers, wherein the source/drain liner is selectively etchable relative to the gate liner, and forming a source/drain cap on the source/drain liner.

BACKGROUND Technical Field

The present invention generally relates to field effect transistordevices, and more particularly to gate and source/drain contactstructures of field effect transistor devices.

Description of the Related Art

A Field Effect Transistor (FET) typically has a source, a channel, and adrain, where current flows from the source to the drain, and a gate thatcontrols the flow of current through the device channel. Field EffectTransistors (FETs) can have a variety of different structures, forexample, FETs have been fabricated with the source, channel, and drainformed in the substrate material itself, where the current flowshorizontally (i.e., in the plane of the substrate), and FinFETs havebeen formed with the channel extending outward from the substrate, butwhere the current also flows horizontally from a source to a drain. Thechannel for the FinFET can be an upright slab of thin rectangularsilicon (Si), commonly referred to as the fin with a gate on the fin, ascompared to a MOSFET with a single gate parallel with the plane of thesubstrate. Depending on the doping of the source and drain, an n-FET ora p-FET can be formed. Two FETs also can be coupled to form acomplementary metal oxide semiconductor (CMOS) device, where a p-channelMOSFET and n-channel MOSFET are electrically coupled together.

SUMMARY

In accordance with an embodiment of the present invention, a method offorming a transistor device is provided. The method includes forming aplurality of gate structures including a gate spacer and a gateelectrode on a substrate, wherein the plurality of gate structures areseparated from each other by a source/drain contact. The method furtherincludes reducing the height of the gate electrodes to form gatetroughs, and forming a gate liner on the gate electrodes and gatespacers. The method further includes forming a gate cap on the gateliner, and reducing the height of the source/drain contacts between thegate structures to form a source/drain trough. The method furtherincludes forming a source/drain liner on the source/drain contacts andgate spacers, wherein the source/drain liner is selectively etchablerelative to the gate liner, and forming a source/drain cap on thesource/drain liner.

In accordance with another embodiment of the present invention, a methodof forming a transistor device is provided. The method includes forminga plurality of gate structures including a gate spacer and a gateelectrode on a substrate, wherein the plurality of gate structures areseparated from each other by a source/drain contact. The method furtherincludes reducing the height of the gate electrodes to form gatetroughs, and forming a gate liner on the gate electrodes and gatespacers. The method further includes forming a gate cap on the gateliner, and reducing the height of the source/drain contacts between thegate structures to form a source/drain trough. The method furtherincludes forming a source/drain liner on the source/drain contacts andgate spacers, wherein the source/drain liner is selectively etchablerelative to the gate liner, and forming a source/drain cap on thesource/drain liner. The method further includes forming a patternedlower mask layer on the source/drain caps and gate caps, wherein asource/drain trench exposes a portion of each of the source/drain capsin a staggered arrangement, and removing the exposed portions of thesource/drain caps, and the underlying portions of the source/drainliners.

In accordance with yet another embodiment of the present invention, atransistor device is provided. The device includes at least three gatestructures including a gate spacer and a gate electrode on a substrate,and a source/drain contact between each pair of the at least three gatestructures. The device further includes a gate contact on the gateelectrode, wherein at least a portion of the gate contact is on aportion of a source/drain cap, and a source/drain lead on each of thesource/drain contacts, wherein a portion of the source/drain lead is ona portion of the gate spacer.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description will provide details of preferred embodimentswith reference to the following figures wherein:

FIG. 1 is a top view showing a plurality of gate structures separated byan interlayer dielectric (ILD) material on source/drains and an activeregion of a substrate, in accordance with an embodiment of the presentinvention;

FIG. 2 is a cross-sectional side view showing a plurality of gatestructures separated by an interlayer dielectric (ILD) material onsource/drains and an active region of a substrate, in accordance with anembodiment of the present invention;

FIG. 3 is a cross-sectional side view showing the gate electrodes of theplurality of gate structures reduced in height to form gate troughs, inaccordance with an embodiment of the present invention;

FIG. 4 is a cross-sectional side view showing a gate liner and a gatecap formed in each of the gate troughs on the gate electrodes, inaccordance with an embodiment of the present invention;

FIG. 5 is a top view showing the gate liner and a gate cap formed withinthe gate spacers of the gate structures, in accordance with anembodiment of the present invention;

FIG. 6 is a cross-sectional side view showing the ILD material removedfrom between each of the gate structures and replaced with a conductivesource/drain contact, in accordance with an embodiment of the presentinvention;

FIG. 7 is a cross-sectional side view showing the conductivesource/drain contacts reduced in height to form source/drain troughs, inaccordance with an embodiment of the present invention;

FIG. 8 is a cross-sectional side view showing a source/drain liner and asource/drain cap formed in each of the source/drain troughs on theconductive source/drain contacts, in accordance with an embodiment ofthe present invention;

FIG. 9 is a top view showing the source/drain liner and source/drain capformed between the gate spacers of the gate structures, in accordancewith an embodiment of the present invention;

FIG. 10 is a cross-sectional side view showing a patterned lower masklayer on the portions of the gate spacers, gate liners, and gate caps,and a patterned upper mask layer on the lower mask layer formingsource/drain trenches, in accordance with an embodiment of the presentinvention;

FIG. 11 is a cross-sectional side view showing the exposed source/draincaps removed from the source/drain liners, in accordance with anembodiment of the present invention;

FIG. 12 is a cross-sectional side view showing exposed portions of thesource/drain liners removed to form source/drain buffers that exposeportions of the conductive source/drain contacts, in accordance with anembodiment of the present invention;

FIG. 13 is a top view showing the portions of the conductivesource/drain contacts, source/drain buffer and gate spacers exposed bythe source/drain trenches, in accordance with an embodiment of thepresent invention;

FIG. 14 is a top view showing the source/drain trenches filled with asecond upper mask layer, and the upper and lower mask layers patternedto form a gate contact trench above a gate cap and gate liner, inaccordance with an embodiment of the present invention;

FIG. 15 is a cross-sectional side view showing the exposed gate cap,gate liner, gate spacer, and portions of the source/drain cap andsource/drain liner exposed by the gate contact trench, in accordancewith an embodiment of the present invention;

FIG. 16 is a cross-sectional side view showing a portion of the exposedgate cap and portions of the source/drain caps removed to expose aportion of the gate liner, in accordance with an embodiment of thepresent invention;

FIG. 17 is a cross-sectional side view showing the exposed portion ofthe gate liner removed to form a gate collar within the gate trough andexpose a portion of the gate electrode, in accordance with an embodimentof the present invention;

FIG. 18 is a cross-sectional side view through the A-A cross-section ofFIG. 20 showing a gate contact formed in the gate trench on the expose aportion of the gate electrode, in accordance with an embodiment of thepresent invention;

FIG. 19 is a cross-sectional side view through the staggered B-Bcross-section of FIG. 20 showing source/drain leads formed in each ofthe source/drain trenches on the expose a portion of the conductivesource/drain contacts, in accordance with an embodiment of the presentinvention; and

FIG. 20 is a top view showing the staggered arrangement of thesource/drain leads and gate contact, in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION

Embodiments of the present invention provide electrical connections togate electrodes and source/drains positioned above the active transistordevices, rather than off-set to a side of the transistor devices, toreduce the footprint size of the transistor devices. A gate contact overan active (GCOA) enables an increase in transistor density on a chipbecause the gate contact is on top of the active region already occupiedby the device, so does not require extra area on the chip. The placementof the gate contact over the active device(s) provides smaller cellsizes for memory and/or logic cells.

Embodiments of the present invention provide a method of fabricatingelectrical connections to gate electrodes and source/drains, where theelectrical connections are positioned above the active transistordevices. Use of different liner and cap materials can provide greateretch selectivity and reduced electrical shorts between closely spacedconductive features. The use of different materials can reducedielectric erosion during subsequent processing steps, so more insulatormaterial remains between the closely spaced conductive features.

Embodiments of the present invention provide a method of overcomingfinite etch selectivity among the different dielectric materials usedfor liners and caps on conductive features of the transistor devices.The use of metal oxides for liner and cap materials along with low-kspacer materials can provide sufficient etch selectivity to meet devicerequirements. Particularly, a low-k spacer is subjected to etchingtwice, once during a source/drain contact etch and another during a gatecontact etch. Thinning/breaching/damaging of the low-k spacer can resultin electrical shorts and/or reliability problem due to widely varyingelectrical characteristics of the devices.

In one or more embodiments, spacer erosion can be sufficiently reducedor eliminated to avoid electrical shorts without forming a dielectriccap over the gate spacer(s), and without recessing the source/draincontacts deeper than the top surface of the gate electrode(s), so thefabrication process complexity can be reduced.

Exemplary applications/uses to which the present invention can beapplied include, but are not limited to: transistor device based memorycells (e.g., static random access memory (SRAM), dynamic random accessmemory (DRAM), latches, etc.), and transistor based logic cells (e.g.,NAND gates, NOR gates, XOR gates, flip-flops, etc.). The transistors canbe planar transistors, FinFETs, nanowire transistors, nanosheettransistors, stacked transistors, etc.

It is to be understood that aspects of the present invention will bedescribed in terms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps can be varied within the scope of aspects of the presentinvention.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a top view of a pluralityof gate structures separated by an interlayer dielectric (ILD) materialon source/drains and an active region of a substrate is shown, inaccordance with an embodiment of the present invention.

In one or more embodiments, one or more gate structures can be formed onan active region of a substrate, where each of the gate structures caninclude a gate spacer 140 around a gate electrode 130. In variousembodiments, the gate electrode 130 can be surrounded by the gate spaceron four sides. The gate electrodes(s) 130 can include a conductive gatefill, a work function layer, and a gate dielectric layer, where the gatedielectric layer can be formed on the device channel(s) and gatespacer(s), the work function layer can be formed on the gate dielectriclayer, and the conductive gate fill can be formed on the work functionlayer. The gate structures can be formed by a combination of conformaland blanket depositions, where the gate dielectric layer and workfunction layer can be formed by conformal depositions, for example,atomic layer deposition (ALD) plasma enhanced ALD (PEALD), or lowpressure chemical vapor deposition (LPCVD), and the conductive gate fillcan be formed by a blanket deposition, for example, chemical vapordeposition (CVD) or plasma enhanced CVD (PECVD).

Patterning techniques such as lithography and etching can be used toform the gate structures. The gate structure can be formed by so-called“gate-first” process in which a gate is formed in the early stage oftransistor fabrication and remains as the final transistor gate).Alternatively, the gate structure can be formed by so-called“replacement gate” process in which a dummy gate is first formed in theearly stage of the transistor fabrication. The dummy gate is thenremoved and replaced by an active gate in the later processing. Thereplacement gate process can replace the entire dummy gate includinggate dielectric and gate electrode, or it can just replace the gateelectrode. The present figures describe a “gate-first” process, but adummy gate could be used.

In various embodiments, the gate spacers 140 can be made of a siliconbased dielectric material, including, but not limited to, silicon oxyboro carbon nitride (SiOBCN), silicon oxy carbo nitride (SiOCN), siliconboro carbonitride (SIBCN), silicon carbonitride (SiCN), siliconoxynitride (SiON), and combinations thereof.

In various embodiments, the active region of the substrate can be avertical fin formed on a substrate or a region of the substrate actingas a device channel.

In one or more embodiments, an interlayer dielectric (ILD) material 150can be blanket deposited on a substrate, so the interlayer dielectric(ILD) material 150 can fill in the spaces between the gate structures.In various embodiments, the interlayer dielectric (ILD) material 150 canbe, for example, silicon oxide (SiO), silicon nitride (SiN), a low-kdielectric material, or any suitable combination of these materials. Alow-k dielectric material can include, but not be limited to, carbondoped silicon oxide (SiO:C), fluorine doped silicon oxide (SiO:F),polymeric material, for example, tetraethyl orthosilicate (TEOS),hydrogen silsesquioxane (HSQ), methylsilsesquioxane (MSQ), siliconcarbide (SiC), silicon oxynitride (SiON), silicon-carbon-nitride (SiCN),boron nitride (BN), silicon boron nitride (SiBN), silicon boroncarbonitride (SiBCN), silicon oxycabonitride (SiOCN), and combinationsthereof.

FIG. 2 is a cross-sectional side view showing a plurality of gatestructures separated by an interlayer dielectric (ILD) material onsource/drains and an active region of a substrate, in accordance with anembodiment of the present invention.

In one or more embodiments, a substrate 110 can be, for example, asingle crystal semiconductor material wafer or asemiconductor-on-insulator stacked wafer. The substrate 110 can includea support layer that provides structural support, and an activesemiconductor layer that can form devices, for example, vertical finsand/or MOSFET device channels. An insulating layer (e.g., a buried oxide(BOX) layer) may be between the active semiconductor layer and thesupport layer to form a semiconductor-on-insulator substrate (SeOI)(e.g., a silicon-on-insulator substrate (SOI)).

In one or more embodiments, the substrate 110 or an active semiconductorlayer can be a crystalline semiconductor, for example, a IV or IV-IVsemiconductor (e.g., silicon (Si), silicon carbide (SiC),silicon-germanium (SiGe), germanium (Ge)) or a III-V semiconductor(e.g., gallium-arsenide (GaAs), indium-phosphide (InP),indium-antimonide (InSb)). In various embodiments, the substrate 110 canbe a single crystal wafer.

In one or more embodiments, the active region can include one or morevertical fins or metal-oxide-semiconductor field effect transistor(MOSFET) device channels formed on the substrate 110. The vertical finscan be formed by a multiple patterning fabrication process, for example,a sidewall image transfer (SIT) process, a self-aligned doublepatterning (SADP) process, self-aligned triple patterning (SATP)process, or a self-aligned quadruple patterning (SAQP). The verticalfins may be formed by a direct write process or double patterningprocess using, for example, immersion lithography, extreme ultravioletlithography, or x-ray lithography. The fin templates can be formed onthe vertical fins, as part of the patterning process. The MOSFET devicechannels can be formed between source/drains formed in the active regionof the substrate. The transistors can be planar transistors, FinFETs,nanowire transistors, nanosheet transistors, stacked transistors, etc.

In one or more embodiments, source/drains 120 can be formed at thesurface of the substrate 110, or on the vertical fins of the activeregion, where the source/drains 120 can be formed for example, byimplantation and/or an epitaxial or heteroepitaxial growth process, forexample, solid phase epitaxy (SPE), molecular beam epitaxy (MBE), liquidphase epitaxy (LPE), or gas phase epitaxy (GPE). The source/drains 120can be doped to be an n-type source/drains or a p-type source/drains,where the dopant(s) can be introduced in situ (i.e., during formation ofa layer) or ex situ (i.e., after formation of a layer). In variousembodiments, n-type dopants can be, for example, phosphorus (P) orarsenic (As), and p-type dopants can be, for example, boron (B) orgallium (Ga). In various embodiments, the source/drains 120 can be asemiconductor material, including, but not limited to n-type (e.g., P orAs) doped silicon (Si) or p-type (e.g., B) doped silicon-germanium(SiGe). In some embodiments, the source/drain material can furthercomprise carbon. The source/drains 120 can be the same semiconductormaterial as the substrate 110 or a different material.

In various embodiments, the gate dielectric layer can be in physicalcontact with the top surface of the active region of the substrate 110,for example, a section of the substrate between two source/drains 120forming a device channel, or on a segment of a vertical fin.

In various embodiments, the gate electrodes(s) 130 can have a height ina range of about 15 nanometers (nm) to about 100 nm, or about 25 nm toabout 40 nm, although other heights are also contemplated.

FIG. 3 is a cross-sectional side view showing the gate electrodes of theplurality of gate structures reduced in height to form gate troughs, inaccordance with an embodiment of the present invention.

In one or more embodiments, the heights of the gate electrodes 130 ofthe gate structures can be reduced in height to form gate troughs 135,where portions of the conductive gate fill and work function layer canbe removed using a directional etch (e.g., reactive ion etch (RIE))and/or isotropic etch (e.g., wet chemical etch, dry plasma etch). Insome embodiments, portions of the gate dielectric layer, when present onthe sidewalls of the spacers, can also be removed.

In various embodiments, the gate troughs 135 can have a depth in a rangeof about 15 nanometers (nm) to about 60 nm, or about 20 nm to about 40nm, although other depths are also contemplated. The depth of gatetroughs 135 can be less than half the height of the gate electrodes.

FIG. 4 is a cross-sectional side view showing a gate liner and a gatecap formed in each of the gate troughs on the gate electrodes, inaccordance with an embodiment of the present invention.

In one or more embodiments, a gate liner 160 can be formed in the gatetrough 135, where the gate liner 160 can be formed by a conformaldeposition (e.g., ALD, PEALD, LPCVD).

In various embodiments, the gate liner 160 can be made of aluminum oxide(AlO), transition metal oxides, for example, hafnium oxide (HfO),zirconium oxide (ZrO), hafnium zirconium oxide (HfZrO), titanium oxide(TiO), tantalum oxide (TaO), niobium oxide (NbO), and combinationsthereof.

In various embodiments, the gate liner 160 can have a thickness in arange of about 2 nm to about 4 nm, or about 3 nm, although otherthicknesses are also contemplated. In various embodiments, the gateliner 160 can be a bilayer, where two separate layers of differentmaterials are formed on each other, with each layer having a thicknessof about 2 nm.

In one or more embodiments, a gate cap 170 can be formed on the gateliner 160, where the gate cap 170 can be formed by a blanket, conformal,or directional deposition (e.g., ALD, PEALD, CVD, PECVD, high densityplasma deposition (HDP), and/or physical vapor deposition (PVD)), tofill in the remaining portion of the gate trough 135, and excessmaterial can be removed using a chemical-mechanical polishing (CMP). Thetop surfaces of the gate cap 170 and gate liner 160 can be approximatelycoplanar with the top surfaces of the gate spacers 140 and ILD material150.

In various embodiments, the gate cap 170 can be a hardmask material,including, but not limited to, silicon nitride (SiN), silicon oxynitride(SiON), silicon carbide (SiC), silicon carbonitride (SiCN), siliconboronitride (SiBN), silicon borocarbide (SiBC), silicon borocarbonitride (SiBCN), or combinations thereof.

FIG. 5 is a top view showing the gate liner and a gate cap formed withinthe gate spacers of the gate structures, in accordance with anembodiment of the present invention.

In one or more embodiments, the gate liner 160 can be on five sides ofthe gate cap 170, where the gate liner can be on the top surface of thegate electrode, including the gate dielectric layer, work functionlayer, and conductive gate fill. The gate spacer 140 can be around thegate liner 160 and gate cap 170.

FIG. 6 is a cross-sectional side view showing the ILD material removedfrom between each of the gate structures and replaced with a conductivesource/drain contact, in accordance with an embodiment of the presentinvention.

In one or more embodiments, portions of the ILD material 150 and gatecaps 170, gate liners 160, and gate spacers 140 can be masked using alithographic mask layer that exposes portions of the ILD material 150between the gate spacers 140 of the gate structures. In variousembodiments, the exposed portions of the ILD material 150 can be removedusing a directional etch, isotropic etch, or a combination thereof toexpose the underlying source/drain(s) 120.

In one or more embodiments, a conductive source/drain contact 180 can beformed in the space left open by removing the ILD material 150, wherethe conductive source/drain contact 180 can be formed by a blanketdeposition, and excess material removed using a CMP. The conductivesource/drain contact 180 can be in physical and electrical contact withthe underlying source/drain 120. A long dimension of conductivesource/drain contacts 180 can be less than the gate structures.

In various embodiments, the conductive source/drain contact 180 can be aconductive metal, including, but not limited to, tungsten (W), aluminum(Al), copper (Cu), cobalt (Co), nickel (Ni), titanium (Ti), ruthenium(Ru), molybdenum (Mo), or any other suitable conductive material. Thecontact can further include a barrier layer. The barrier layer can betitanium nitride (TiN), tantalum nitride (TaN), hafnium nitride (HfN),niobium nitride (NbN), tungsten nitride (WN), tungsten carbon nitride(WCN), or combinations thereof, where the barrier layer can preventdiffusion and/or alloying of the conductive metal contact fill materialwith the top source drain material, and/or anode/cathode material. Invarious embodiments, the barrier layer can be deposited in thetrench(es) by ALD, CVD, metal-organic CVD (MOCVD), PECVD, orcombinations thereof. In various embodiments, the metal fill can beformed by ALD, CVD, and/or PVD to form the conductive source/draincontact 180.

FIG. 7 is a cross-sectional side view showing the conductivesource/drain contacts reduced in height to form source/drain troughs, inaccordance with an embodiment of the present invention.

In one or more embodiments, the height of the conductive source/draincontact 180 can be reduced to form source/drain troughs 185, where aportion of the conductive source/drain contact 180 can be removed usinga directional etch (e.g., reactive ion etch (RIE)) and/or isotropic etch(e.g., wet chemical etch, dry plasma etch).

In various embodiments, the depth of the source/drain troughs 185 canhave a depth in a range of about 10 nm to about 40 nm, or about 20 nm toabout 30 nm, although other depths are also contemplated. The depth ofthe source/drain troughs 185 can be less than the depth of the gatetroughs 135, or about the same as the gate troughs 135. In variousembodiments, the top surfaces of the reduced height conductivesource/drain contact 180 can be above the bottom surface of the adjacentgate caps 170.

FIG. 8 is a cross-sectional side view showing a source/drain liner and asource/drain cap formed in each of the source/drain troughs on theconductive source/drain contacts, in accordance with an embodiment ofthe present invention.

In one or more embodiments, a source/drain liner 190 can be formed ineach of the source/drain troughs 185, where the source/drain liner 190can be formed by a conformal deposition (e.g., ALD, PEALD, LPCVD). Thesource/drain liner 190 can be formed on the sidewalls of the gatespacers 140 and the top surface of the conductive source/drain contact180.

In various embodiments, the source/drain liner 190 can have a thicknessin a range of about 2 nm to about 4 nm, or about 3 nm, although otherthicknesses are also contemplated. In various embodiments, the gateliner 160 can be a bilayer, where two separate layers of differentmaterials are formed on each other, with each layer having a thicknessof about 2 nm.

In various embodiments, the source/drain liner 190 can be aluminum oxide(AlO), transition metal binary oxides, for example, hafnium oxide (HfO),zirconium oxide (ZrO), hafnium zirconium oxide (HfZrO), titanium oxide(TiO), tantalum oxide (TaO), niobium oxide (NbO), and combinationsthereof, where the source/drain liner 190 can be a different materialfrom the gate liners 160, so the source/drain liner 190 can beselectively removed.

In one or more embodiments, a source/drain cap 200 can be formed on thesource/drain liner 190, where the source/drain cap 200 can be formed bya blanket deposition (e.g., ALD, CVD, PECVD, HDP, PVD), to fill in theremaining portion of the source/drain trough 185, and excess materialcan be removed using a chemical-mechanical polishing (CMP). The topsurfaces of the source/drain cap 200 and source/drain liner 190 can beapproximately coplanar with the top surfaces of the gate cap 170, gateliner 160, gate spacers 140 and ILD material 150.

In various embodiments, the source/drain cap 200 can be a hardmaskmaterial, including, but not limited to, silicon nitride (SiN), siliconoxynitride (SiON), silicon carbide (SiC), silicon carbonitride (SiCN),silicon boronitride (SiBN), silicon borocarbide (SiBC), silicon borocarbonitride (SiBCN), or combinations thereof. In various embodiments,the source/drain cap 200 can be a different hardmask material from thegate cap 170, so the source/drain cap 200 can be selectively removed.

In a non-limiting exemplary embodiments, the gate liner 160 can behafnium oxide (HfO), the gate cap 170 can be silicon nitride (SiN), thesource/drain liner 190 can be aluminum oxide (AlO), and the source/draincap 200 can be silicon carbide (SiC), so selective removal of thesource/drain cap 200 and source/drain liner 190 reduces the amount oferosion of the gate cap 170.

FIG. 9 is a top view showing the source/drain liner and source/drain capformed between the gate spacers of the gate structures, in accordancewith an embodiment of the present invention.

In one or more embodiments, the source/drain liners 190 and source/draincaps 200 are formed between the gate spacers 140 of the gate structures,where the source/drain liners 190 and source/drain caps 200 may notextend to the end walls of the gate spacers 140.

In one or more embodiments, the source/drain liner 190 can be on fivesides of the source/drain cap 200, where the source/drain liner 190 canbe on the top surface of the conductive source/drain contact 180. Thegate spacer 140 can be on opposite sides of the source/drain liner 190and source/drain cap 200. The ILD material 150 can be on opposite sidesof the source/drain liner.

FIG. 10 is a cross-sectional side view showing a patterned lower masklayer on the portions of the gate spacers, gate liners, and gate caps,and a patterned upper mask layer on the lower mask layer formingsource/drain trenches, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a lower mask layer 210 can be formed on theportions of the gate spacers 140, gate liners 160, and gate caps 170,source/drain liners 190, and source/drain caps 200. An upper mask layer220 can be formed on the lower mask layer 210.

In various embodiments, the lower mask layer 210 can be a hardmaskmaterial (e.g., silicon oxide (SiO)) that is blanket deposited on theexposed surfaces, and the upper mask layer 220 can be a lithographicresist material or a stack of lithographic materials such as organicplanarization layer (OPL), anti-reflection coating (ARC), andphotoresist layer. The upper mask layer 220 can be patterned usinglithographic techniques and etching, and exposed portion of the lowermask layer 210 can be removed using a selective directional etch (e.g.,RIE) to form source/drain trenches 222, where the source/drain trenches222 can be positioned to expose at least portions of the source/drainliner 190 and source/drain cap 200, and may expose portions of the gatespacers 140, gate liners 160, and gate caps 170. The source/draintrenches 222 do not need to be precisely placed over the source/drainliner 190 and source/drain cap 200 because the etch selectivity of thegate liners 160 and gate caps 170 can protect the conductivesource/drain contact 180 during a removal process. The source/draintrenches 222 can be wider than the source/drain liners 190 andsource/drain caps.

FIG. 11 is a cross-sectional side view showing the exposed source/draincaps removed from the source/drain liners, in accordance with anembodiment of the present invention.

In one or more embodiments, the exposed source/drain caps 200 can beremoved from within the source/drain liners 190 to expose the underlyingsource/drain liners 190. In various embodiments, the source/drain caps200 can be removed using a selective directional etch (e.g., RIE) or aselective isotropic etch (e.g., wet chemical etch, dry plasma), whereduring the etch a portion of exposed gate spacers may be removed to formspacer dimples 143, and a portion of exposed gate caps 170 may beremoved to form cap recesses 173. In various embodiments, thesource/drain caps 200 can be removed selective to the source/drainliners 190 and gate liner 160.

In various embodiments, the gate liner 160 and source/drain liner 190can remain after removing the source/drain cap 200. In variousembodiments, the exposed portions of the gate spacers 140 can experiencea concave dimpling due to partial erosion of the gate spacer materialduring selective etching, where upper portions of the sidewalls of thegate spacers 140 are protected by the gate liner 160 and thesource/drain liner 190. The source/drain liner 190 can protect theconductive source/drain contact 180.

FIG. 12 is a cross-sectional side view showing exposed portions of thesource/drain liners removed to form source/drain buffers that exposeportions of the conductive source/drain contacts, in accordance with anembodiment of the present invention.

In one or more embodiments, a portion of the source/drain liners 190 onthe conductive source/drain contacts 180 can be removed using aselective, directional etch (e.g., RIE) to expose the top surface of theconductive source/drain contacts 180, and leave a source/drain buffer195 on each of the sidewalls of the opposite gate spacers 140. Theendwalls of the source/drain liners 190 adjoining the ILD material 150may not be exposed by the source/drain trenches 222, so that portion ofthe source/drain liners 190 may not be etched, and the unexposedportions of the source/drain liners 190 can remain.

In one or more embodiments, a portion of the source/drain liners 190 onthe conductive source/drain contacts 180 can be removed using aselective, isotropic etch (e.g., wet etch ultra dilute hydrofluoric acid(HF), or dry plasma sulfur hexafluoride (SF₆)) to remove all of theexposed source/drain liners 190, and expose the top surface of theconductive source/drain contacts 180 and portions of the sidewalls ofthe gate spacers 140. Etch processes can be selective for linermaterial.

FIG. 13 is a top view showing the portions of the conductivesource/drain contacts, source/drain buffer and gate spacers exposed bythe source/drain trenches, in accordance with an embodiment of thepresent invention.

In various embodiments, the source/drain trenches 222 formed overportions of adjacent source/drain caps 200 can be staggered, so thesource/drain trenches 222 are not on directly opposite sides of gatecaps 170. The source/drain trenches 222 can have different sizes, anddifferent portions of the gate spacers 140 and gate liners 160 may beexposed by each of the source/drain trenches 222.

FIG. 14 is a top view showing the source/drain trenches filled with asecond upper mask layer, and the upper and lower mask layers patternedto form a gate contact trench above a gate cap and gate liner, inaccordance with an embodiment of the present invention.

In one or more embodiments, the source/drain trenches 222 can be filledwith additional lithographic material, such as organic planarizationlayer (OPL), and the upper mask layer 220 and lower mask layer 210 canbe further patterned and removed to form gate trenches 227 over portionsof the gate caps 170 and gate liners 160.

In various embodiments, the gate trenches 227 may be different sizes ormay shift, so that different portions of the gate spacers 140, gate caps170, and gate liners 160 may be exposed by each of the gate trenches227. The gate trenches 227 can be off-set from the source/drain trenches222.

FIG. 15 is a cross-sectional side view showing the exposed gate cap,gate liner, gate spacer, and portions of the source/drain cap andsource/drain liner exposed by the gate contact trench, in accordancewith an embodiment of the present invention.

In one or more embodiments, the upper and lower mask layers can bepatterned and removed using a directional etch to expose the underlyingportion of the gate caps 170, as well as portions of the gate liner 160and gate spacers 140. In a various embodiments, the gate cap removalprocess is selective to the gate liners 160 and source/drain cap 190.

FIG. 16 is a cross-sectional side view showing a portion of the exposedgate cap and portions of the source/drain caps removed to expose aportion of the gate liner, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a selective etch can be used to remove theexposed portions of the gate caps 170 to expose the underlying portionof the gate liner 160.

FIG. 17 is a cross-sectional side view showing the exposed portion ofthe gate liner removed to form a gate collar within the gate trough andexpose a portion of the gate electrode, in accordance with an embodimentof the present invention.

In one or more embodiments, a portion of the gate liners 160 on the gateelectrodes 130 can be removed using a selective, directional etch (e.g.,RIE) to expose the top surface of the gate electrode 130, and leave agate buffer 165 on each of the sidewalls of the opposite gate spacers140. The endwalls of the gate liners 160 may not be exposed by the gatetrenches 227, so that portion of the gate liners 160 may not be etched.

In one or more embodiments, a portion of the gate liners 160 on the gateelectrodes 130 can be removed using a selective, isotropic etch (e.g.,wet etch ultra dilute hydrofluoric acid (HF), or dry plasma SF₆) toremove all of the exposed gate liners 160.

FIG. 18 is a cross-sectional side view through the A-A cross-section ofFIG. 20 showing a gate contact formed in the gate trench on the expose aportion of the gate electrode, in accordance with an embodiment of thepresent invention.

In one or more embodiments, the upper mask layer 220 can be removed andthe source/drain trenches 222 reopened using a selective etch.

In one or more embodiments, the source/drain trenches 222 and gatetrenches 227 can be filled with a conductive material at the same time.A gate contact 230 can be formed in each of the gate trenches 227 on theexpose a portion of the gate electrode 130.

FIG. 19 is a cross-sectional side view through the staggered B-Bcross-section of FIG. 20 showing source/drain leads formed in each ofthe source/drain trenches on the expose a portion of the conductivesource/drain contacts, in accordance with an embodiment of the presentinvention.

In one or more embodiments, a source/drain lead 235 can be formed ineach of the source/drain trenches 222 on the expose a portion of theconductive source/drain contacts 180.

In various embodiments, the gate contacts 230 and source/drain leads 235can be a conductive metal, including, but not limited to, tungsten (W),aluminum (Al), copper (Cu), cobalt (Co), nickel (Ni), titanium (Ti),ruthenium (Ru), molybdenum (Mo), or any other suitable conductivematerial. The contact can further include a barrier layer. The barrierlayer can be titanium nitride (TiN), tantalum nitride (TaN), hafniumnitride (HfN), niobium nitride (NbN), tungsten nitride (WN), tungstencarbon nitride (WCN), or combinations thereof, where the barrier layercan prevent diffusion and/or alloying of the metal contact fill materialwith the top source drain material, and/or anode/cathode material. Invarious embodiments, the barrier layer can be deposited in thetrench(es) by ALD, CVD, MOCVD, PECVD, or combinations thereof. Invarious embodiments, the metal fill can be formed by ALD, CVD, and/orPVD to form the electrical contacts.

FIG. 20 is a top view showing the staggered arrangement of thesource/drain leads and gate contact, in accordance with an embodiment ofthe present invention.

In one or more embodiments, placement of the gate contacts 230 andsource/drain leads 235 can be above the active devices, where thepositions of the source/drain leads 235 can be offset from the positionsof the gate contacts 230 and each other to maximize the dielectricmaterial between the conductive material to avoid electrical shorts.

In various embodiments, portions of the gate liners 160 can remain inregions of the gate troughs 135 outside of the gate trenches 227, andportions of the source/drain liner 190 can remain in regions of thesource/drain troughs 185 outside of the source/drain trenches 222. Theseparate liners 160, 190 can be around the bottom surface and sidewallsof the gate cap 170 and source/drain cap 200 in regions outside of thegate trenches 227 and source/drain trenches 222, respectively, toimprove the Gate Contact Over Active (CGOA) margin and self-alignedcontacts (SAC). Even with mask misalignments, the combination of gateliners 160 and gate caps 170, and source/drain liners 190 andsource/drain caps 200, can protect the gate spacers 140 and conductivesource/drain contacts 180. The avoidance of excessive etching of thegate caps 170 and source/drain caps 200 can improve device reliabilityby reducing electrical shorts between the source/drain and gatestructures.

The present embodiments can include a design for an integrated circuitchip, which can be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer can transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein can be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case, the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiGe. These compounds includedifferent proportions of the elements within the compound, e.g., SiGeincludes Si_(x)Ge_(1-x) where x is less than or equal to 1, etc. Inaddition, other elements can be included in the compound and stillfunction in accordance with the present principles. The compounds withadditional elements will be referred to herein as alloys.

Reference in the specification to “one embodiment” or “an embodiment”,as well as other variations thereof, means that a particular feature,structure, characteristic, and so forth described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “in one embodiment” or “in an embodiment”, as well anyother variations, appearing in various places throughout thespecification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This can be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, can be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGs. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGS. For example, if the device in theFIGS. is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (rotated 90degrees or at other orientations), and the spatially relativedescriptors used herein can be interpreted accordingly. In addition, itwill also be understood that when a layer is referred to as being“between” two layers, it can be the only layer between the two layers,or one or more intervening layers can also be present.

It will be understood that, although the terms first, second, etc. canbe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements can also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

Having described preferred embodiments of a device and method offabricating the device (which are intended to be illustrative and notlimiting), it is noted that modifications and variations can be made bypersons skilled in the art in light of the above teachings. It istherefore to be understood that changes may be made in the particularembodiments disclosed which are within the scope of the invention asoutlined by the appended claims. Having thus described aspects of theinvention, with the details and particularity required by the patentlaws, what is claimed and desired protected by Letters Patent is setforth in the appended claims.

What is claimed is:
 1. A method of forming a transistor device,comprising: forming a plurality of gate structures including a gatespacer and a gate electrode on a substrate, wherein the plurality ofgate structures are separated from each other by a source/drain contact;reducing the height of the gate electrodes to form gate troughs; forminga gate liner on the gate electrodes and gate spacers; forming a gate capon the gate liner; reducing the height of the source/drain contactsbetween the gate structures to form a source/drain trough; forming asource/drain liner on the source/drain contacts and gate spacers,wherein the source/drain liner is selectively etchable relative to thegate liner; and forming a source/drain cap on the source/drain liner. 2.The method of claim 1, wherein source/drains are in the substrate, andeach of the source/drain contacts is in electrical contact with one ofthe source/drains.
 3. The method of claim 1, further comprising forminga patterned lower mask layer on at least a portion of the gate caps andgate liners, wherein a portion of the source/drain caps and source/drainliners are exposed.
 4. The method of claim 3, further comprisingremoving the exposed portion of the source/drain caps, and removing aportion of the source/drain liners.
 5. The method of claim 1, furthercomprising forming a patterned lower mask layer on at least a portion ofthe source/drain caps and source/drain liners, wherein a portion of thegate caps and gate liners are exposed.
 6. The method of claim 5, furthercomprising removing the exposed portion of the gate caps, and removing aportion of the gate liners.
 7. The method of claim 1, wherein thesource/drain liners are a metal oxide selected from the group consistingof aluminum oxide (AlO), hafnium oxide (HfO), zirconium oxide (ZrO),titanium oxide (TiO), tantalum oxide (TaO), niobium oxide (NbO), andcombinations thereof.
 8. The method of claim 7, wherein the gate linersare a metal oxide selected from the group consisting of aluminum oxide(AlO), hafnium oxide (HfO), zirconium oxide (ZrO), titanium oxide (TiO),tantalum oxide (TaO), niobium oxide (NbO), and combinations thereof, andthe gate liners are a different metal oxide from the source/drainliners.
 9. The method of claim 8, wherein the gate caps are a hardmaskmaterial selected from the group consisting of silicon nitride (SiN),silicon oxynitride (SiON), silicon carbide (SiC), silicon carbonitride(SiCN), silicon boronitride (SiBN), silicon borocarbide (SiBC), siliconboro carbonitride (SiBCN), and combinations thereof.
 10. The method ofclaim 9, wherein the source/drain caps are a hardmask material selectedfrom the group consisting of silicon nitride (SiN), silicon oxynitride(SiON), silicon carbide (SiC), silicon carbonitride (SiCN), siliconboronitride (SiBN), silicon borocarbide (SiBC), silicon borocarbonitride (SiBCN), and combinations thereof, and the gate caps are adifferent hardmask material from the source/drain caps.
 11. The methodof claim 10, wherein the gate spacers are a silicon based dielectricmaterial selected from the group consisting of silicon oxy boro carbonnitride (SiOBCN), silicon oxy carbo nitride (SiOCN), silicon borocarbonitride (SIBCN), silicon carbonitride (SiCN), and combinationsthereof.
 12. A method of forming a transistor device, comprising:forming a plurality of gate structures including a gate spacer and agate electrode on a substrate, wherein the plurality of gate structuresare separated from each other by a source/drain contact; reducing theheight of the gate electrodes to form gate troughs; forming a gate lineron the gate electrodes and gate spacers; forming a gate cap on the gateliner; reducing the height of the source/drain contacts between the gatestructures to form a source/drain trough; forming a source/drain lineron the source/drain contacts and gate spacers, wherein the source/drainliner is selectively etchable relative to the gate liner; forming asource/drain cap on the source/drain liner; forming a patterned lowermask layer on the source/drain caps and gate caps, wherein asource/drain trench exposes a portion of each of the source/drain capsin a staggered arrangement; and removing the exposed portions of thesource/drain caps, and the underlying portions of the source/drainliners.
 13. The method of claim 12, further comprising forming asource/drain lead in each of the source/drain trenches.
 14. The methodof claim 13, further comprising forming at least one gate trench in thelower mask layer that exposes a portion of at least one of the gatecaps; and removing the exposed portion of the at least one gate cap, andthe underlying portion of the gate liner.
 15. The method of claim 14,further comprising forming a gate contact in the at least one gatetrench.